Brushhead assembly systems for power toothbrushes with a back-and-forth, sweeping brush member motion typically include a drive train member (drive beam) and a brushhead with brush member which can together vary in stiffness, center of gravity and mass, all of which affect the resonant frequency of the brushhead assembly system. Because of the relatively thin geometry and the flexible material, typically plastic, used in many such brushheads, the resonant frequency of the brushhead assembly system is frequently between 100-250 Hz, within which range may be the operating/drive frequency of the power toothbrush.
This relationship between the drive frequency of the toothbrush and the resonant frequency of the brushhead assembly system may in some cases be helpful, producing larger sweeping amplitudes with relatively small mechanical driver motion. However, it can also be detrimental if the resonant frequency is too close to the drive frequency, which results in excessive amplitudes of the brush member, i.e. up to 9 mm, which is both difficult to control and potentially harmful to the user.
Hence, there is a need for a brushhead assembly system which includes a portion which can be conveniently tuned so as to shift the resonant frequency of the brushhead assembly system up or down relative to the drive frequency to control the amplitude of brush member movement to be within a desired range. This allows for the use of a larger tolerance range of flexible brushheads, without the necessity of a high degree of control over the manufacture of the various parts of the brushhead assembly system.